Patient selectable knee arthroplasty devices

ABSTRACT

Disclosed herein are methods and devices for repairing articular surfaces in a knee joint. The articular surface repairs are customizable or highly selectable for each patient and geared toward providing optimal fit and function. Kits are also provided to enable customized repairs to be performed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of U.S. Ser. No. 10/724,010 filed Nov.25, 2003 entitled “PATIENT SELECTABLE JOINT ARTHROPLASTY DEVICES ANDSURGICAL TOOLS FACILITATING INCREASED ACCURACY, SPEED AND SIMPLICITY INPERFORMING TOTAL AND PARTIAL JOINT ARTHROPLASTY,” which is acontinuation-in-part of U.S. Ser. No. 10/305,652 entitled “METHODS ANDCOMPOSITIONS FOR ARTICULAR REPAIR,” filed Nov. 27, 2002, which is acontinuation-in-part of U.S. Ser. No. 10/160,667, filed May 28, 2002,which in turn claims the benefit of U.S. Ser. No. 60/293,488 entitled“METHODS TO IMPROVE CARTILAGE REPAIR SYSTEMS”, filed May 25, 2001, U.S.Ser. No. 60/363,527, entitled “NOVEL DEVICES FOR CARTILAGE REPAIR, filedMar. 12, 2002 and U.S. Ser. Nos. 60/380,695 and 60/380,692, entitled“METHODS AND COMPOSITIONS FOR CARTILAGE REPAIR,” and “METHODS FOR JOINTREPAIR,” filed May 14, 2002, all of which applications are herebyincorporated by reference in their entireties.

This application is also a continuation-in-part of U.S. application Ser.No. 10/681,750 filed Oct. 7, 2003 entitled “MINIMALLY INVASIVE JOINTIMPLANT WITH 3-DIMENSIONAL GEOMETRY MATCHING THE ARTICULAR SURFACES.”

FIELD OF THE INVENTION

The present invention relates to orthopedic methods, systems and devicesand more particularly relates to methods, systems and devices forarticular resurfacing in the knee.

BACKGROUND OF THE INVENTION

There are various types of cartilage, e.g., hyaline cartilage andfibrocartilage. Hyaline cartilage is found at the articular surfaces ofbones, e.g., in the joints, and is responsible for providing the smoothgliding motion characteristic of moveable joints. Articular cartilage isfirmly attached to the underlying bones and measures typically less than5 mm in thickness in human joints, with considerable variation dependingon the joint and the site within the joint.

Adult cartilage has a limited ability of repair; thus, damage tocartilage produced by disease, such as rheumatoid and/or osteoarthritis,or trauma can lead to serious physical deformity and debilitation.Furthermore, as human articular cartilage ages, its tensile propertieschange. The superficial zone of the knee articular cartilage exhibits anincrease in tensile strength up to the third decade of life, after whichit decreases markedly with age as detectable damage to type II collagenoccurs at the articular surface. The deep zone cartilage also exhibits aprogressive decrease in tensile strength with increasing age, althoughcollagen content does not appear to decrease. These observationsindicate that there are changes in mechanical and, hence, structuralorganization of cartilage with aging that, if sufficiently developed,can predispose cartilage to traumatic damage.

Once damage occurs, joint repair can be addressed through a number ofapproaches. One approach includes the use of matrices, tissue scaffoldsor other carriers implanted with cells (e.g., chondrocytes, chondrocyteprogenitors, stromal cells, mesenchymal stem cells, etc.). Thesesolutions have been described as a potential treatment for cartilage andmeniscal repair or replacement. See, also, International Publications WO99/51719 to Fofonoff, published Oct. 14, 1999; WO01/91672 to Simon etal., published Dec. 6, 2001; and WO01/17463 to Mannsmann, published Mar.15, 2001; U.S. Pat. No. 6,283,980 B1 to Vibe-Hansen et al., issued Sep.4, 2001, U.S. Pat. No. 5,842,477 to Naughton issued Dec. 1, 1998, U.S.Pat. No. 5,769,899 to Schwartz et al. issued Jun. 23, 1998, U.S. Pat.No. 4,609,551 to Caplan et al. issued Sep. 2, 1986, U.S. Pat. No.5,041,138 to Vacanti et al. issued Aug. 29, 1991, U.S. Pat. No.5,197,985 to Caplan et al. issued Mar. 30, 1993, U.S. Pat. No. 5,226,914to Caplan et al. issued Jul. 13, 1993, U.S. Pat. No. 6,328,765 toHardwick et al. issued Dec. 11, 2001, U.S. Pat. No. 6,281,195 to Ruegeret al. issued Aug. 28, 2001, and U.S. Pat. No. 4,846,835 to Grandeissued Jul. 11, 1989. However, clinical outcomes with biologicreplacement materials such as allograft and autograft systems and tissuescaffolds have been uncertain since most of these materials do notachieve a morphologic arrangement or structure similar to or identicalto that of normal, disease-free human tissue it is intended to replace.Moreover, the mechanical durability of these biologic replacementmaterials remains uncertain.

Usually, severe damage or loss of cartilage is treated by replacement ofthe joint with a prosthetic material, for example, silicone, e.g. forcosmetic repairs, or metal alloys. See, e.g., U.S. Pat. No. 6,383,228 toSchmotzer, issued May 7, 2002; U.S. Pat. No. 6,203,576 to Afriat et al.,issued Mar. 20, 2001; U.S. Pat. No. 6,126,690 to Ateshian, et al.,issued Oct. 3, 2000. Implantation of these prosthetic devices is usuallyassociated with loss of underlying tissue and bone without recovery ofthe full function allowed by the original cartilage and, with somedevices, serious long-term complications associated with the loss ofsignificant amount of tissue and bone can include infection, osteolysisand also loosening of the implant.

Further, joint arthroplasties are highly invasive and require surgicalresection of the entire or the majority of the articular surface of oneor more bones. With these procedures, the marrow space is reamed inorder to fit the stem of the prosthesis. The reaming results in a lossof the patient's bone stock. U.S. Pat. No. 5,593,450 to Scott et al.issued Jan. 14, 1997 discloses an oval domed shaped patella prosthesis.The prosthesis has a femoral component that includes two condyles asarticulating surfaces. The two condyles meet to form a second trochleargroove and ride on a tibial component that articulates with respect tothe femoral component. A patella component is provided to engage thetrochlear groove. U.S. Pat. No. 6,090,144 to Letot et al. issued Jul.18, 2000 discloses a knee prosthesis that includes a tibial componentand a meniscal component that is adapted to be engaged with the tibialcomponent through an asymmetrical engagement.

A variety of materials can be used in replacing a joint with aprosthetic, for example, silicone, e.g. for cosmetic repairs, orsuitable metal alloys are appropriate. See, e.g., U.S. Pat. No.6,443,991 B1 to Running issued Sep. 3, 2002, U.S. Pat. No. 6,387,131 B1to Miehlke et al. issued May 14, 2002; U.S. Pat. No. 6,383,228 toSchmotzer issued May 7, 2002; U.S. Pat. No. 6,344,059 B1 to Krakovits etal. issued Feb. 5, 2002; U.S. Pat. No. 6,203,576 to Afriat et al. issuedMar. 20, 2001; U.S. Pat. No. 6,126,690 to Ateshian et al. issued Oct. 3,2000; U.S. Pat. No. 6,013,103 to Kaufman et al. issued Jan. 11, 2000.Implantation of these prosthetic devices is usually associated with lossof underlying tissue and bone without recovery of the full functionallowed by the original cartilage and, with some devices, seriouslong-term complications associated with the loss of significant amountsof tissue and bone can cause loosening of the implant. One suchcomplication is osteolysis. Once the prosthesis becomes loosened fromthe joint, regardless of the cause, the prosthesis will then need to bereplaced. Since the patient's bone stock is limited, the number ofpossible replacement surgeries is also limited for joint arthroplasty.

As can be appreciated, joint arthroplasties are highly invasive andrequire surgical resection of the entire, or a majority of the,articular surface of one or more bones involved in the repair. Typicallywith these procedures, the marrow space is fairly extensively reamed inorder to fit the stem of the prosthesis within the bone. Reaming resultsin a loss of the patient's bone stock and over time subsequentosteolysis will frequently lead to loosening of the prosthesis. Further,the area where the implant and the bone mate degrades over timerequiring the prosthesis to eventually be replaced. Since the patient'sbone stock is limited, the number of possible replacement surgeries isalso limited for joint arthroplasty. In short, over the course of 15 to20 years, and in some cases even shorter time periods, the patient canrun out of therapeutic options ultimately resulting in a painful,non-functional joint.

U.S. Pat. No. 6,206,927 to Fell, et al., issued Mar. 27, 2001, and U.S.Pat. No. 6,558,421 to Fell, et al., issued May 6, 2003, disclose asurgically implantable knee prosthesis that does not require boneresection. This prosthesis is described as substantially elliptical inshape with one or more straight edges. Accordingly, these devices arenot designed to substantially conform to the actual shape (contour) ofthe remaining cartilage in vivo and/or the underlying bone. Thus,integration of the implant can be extremely difficult due to differencesin thickness and curvature between the patient's surrounding cartilageand/or the underlying subchondral bone and the prosthesis. U.S. Pat. No.6,554,866 to Aicher, et al. issued Apr. 29, 2003 describes amono-condylar knee joint prosthesis.

Interpositional knee devices that are not attached to both the tibia andfemur have been described. For example, Platt et al. (1969) “MouldArthroplasty of the Knee,” Journal of Bone and Joint Surgery51B(1):76-87, describes a hemi-arthroplasty with a convex undersurfacethat was not rigidly attached to the tibia. Devices that are attached tothe bone have also been described. Two attachment designs are commonlyused. The McKeever design is a cross-bar member, shaped like a “t” froma top perspective view, that extends from the bone mating surface of thedevice such that the “t” portion penetrates the bone surface while thesurrounding surface from which the “t” extends abuts the bone surface.See McKeever, “Tibial Plateau Prosthesis,” Chapter 7, p. 86. Analternative attachment design is the Macintosh design, which replacesthe “t” shaped fin for a series of multiple flat serrations or teeth.See Potter, “Arthroplasty of the Knee with Tibial Metallic Implants ofthe McKeever and Macintosh Design,” Surg. Clins. Of North Am. 49(4):903-915 (1969).

U.S. Pat. No. 4,502,161 to Wall issued Mar. 5, 1985, describes aprosthetic meniscus constructed from materials such as silicone rubberor Teflon with reinforcing materials of stainless steel or nylonstrands. U.S. Pat. No. 4,085,466 to Goodfellow et al. issued Mar. 25,1978, describes a meniscal component made from plastic materials.Reconstruction of meniscal lesions has also been attempted withcarbon-fiber-polyurethane-poly (L-lactide). Leeslag, et al., Biologicaland Biomechanical Performance of Biomaterials (Christel et al., eds.)Elsevier Science Publishers B.V., Amsterdam. 1986. pp. 347-352.Reconstruction of meniscal lesions is also possible with bioresorbablematerials and tissue scaffolds.

However, currently available devices do not always provide idealalignment with the articular surfaces and the resultant joint congruity.Poor alignment and poor joint congruity can, for example, lead toinstability of the joint. In the knee joint, instability typicallymanifests as a lateral instability of the joint. Further, none of thesesolutions take into account the fact that roughly 80% of patientsundergoing knee surgery have a healthy lateral compartment and only needto repair the medial condyle and the patella. An additional 10% onlyhave damage to the lateral condyle. Thus, 90% of patients do not requirethe entire condylar surface repaired.

Thus, there remains a need for compositions for joint repair, includingmethods and compositions that facilitate the integration between thecartilage replacement system and the surrounding cartilage which takesinto account the actual damage to be repaired.

SUMMARY OF THE INVENTION

The present invention provides novel devices and methods for replacing aportion (e.g., diseased area and/or area slightly larger than thediseased area) of a knee joint (e.g., cartilage and/or bone) with one ormore implants, where the implant(s) achieves a near anatomic fit withthe surrounding structures and tissues. In cases where the devicesand/or methods include an element associated with the underlyingarticular bone, the invention also provides that the bone-associatedelement achieves a near anatomic alignment with the subchondral bone.The invention also provides for the preparation of an implantation sitewith a single cut, or a few relatively small cuts. The invention alsoprovides a kit which includes one or more implants used to achieveoptimal joint correction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram of a method for assessing a joint in need ofrepair according to the invention wherein the existing joint surface isunaltered, or substantially unaltered, prior to receiving the selectedimplant. FIG. 1B is a block diagram of a method for assessing a joint inneed of repair according to the invention wherein the existing jointsurface is unaltered, or substantially unaltered, prior to designing animplant suitable to achieve the repair.

FIG. 2A is a perspective view of a joint implant of the inventionsuitable for implantation at the tibial plateau of the knee joint. FIG.2B is a top view of the implant of FIG. 2A. FIG. 2C is a cross-sectionalview of the implant of FIG. 2B along the lines C-C shown in FIG. 2B.FIG. 2D is a cross-sectional view along the lines D-D shown in FIG. 2B.FIG. 2E is a cross-sectional view along the lines E-E shown in FIG. 2B.FIG. 2F is a side view of the implant of FIG. 2A. FIG. 2G is across-sectional view of the implant of FIG. 2A shown implanted takenalong a plane parallel to the sagittal plane. FIG. 2H is across-sectional view of the implant of FIG. 2A shown implanted takenalong a plane parallel to the coronal plane. FIG. 2I is across-sectional view of the implant of FIG. 2A shown implanted takenalong a plane parallel to the axial plane. FIG. 2J shows a slightlylarger implant that extends closer to the bone medially (towards theedge of the tibial plateau) and anteriorly and posteriorly. FIG. 2K is aside view of an alternate embodiment of the joint implant of FIG. 2Ashowing an anchor in the form of a keel. FIG. 2L is a bottom view of analternate embodiment of the joint implant of FIG. 2A showing an anchor.FIG. 2M is a side view of an exemplary embodiment of the joint implantof FIG. 2A. FIG. 2N-O are alternative embodiments of the implant showingthe lower surface have a trough for receiving a cross-bar. FIG. 2Pillustrates a variety of cross-bars. FIGS. 2Q-R illustrate the deviceimplanted within a knee joint.

FIGS. 3A and B are perspective views of a joint implant suitable for useon a condyle of the femur from the inferior and superior surfaceviewpoints, respectively. FIG. 3C is a side view of the implant of FIG.3A. FIG. 3D is a view of the inferior surface of the implant; FIG. 3E isa view of the superior surface of the implant and FIG. 3F is across-section of the implant. FIG. 3G is an axial view of a femur withthe implant installed thereon. FIG. 3H is an anterior view of the kneejoint without the patella wherein the implant is installed on thefemoral condyle. FIG. 3I is an anterior view of the knee joint with animplant of FIG. 3A implanted on the femoral condyle along with animplant suitable for the tibial plateau, such as that shown in FIG. 2.

FIGS. 4A-H depict another implant suitable for placement on a femoralcondyle. FIG. 4A is a slightly perspective view of the implant from thesuperior surface. FIG. 4B is a side view of the implant of FIG. 4A. FIG.4C is a top view of the inferior surface of the implant; FIGS. 4D and Eare perspective side views of the implant. FIG. 4F is an axial view of afemur with the implant installed thereon. FIG. 4G is an anterior view ofthe knee joint without the patella wherein the implant is installed onthe femoral condyle. FIG. 4H is an anterior view of the knee joint withan implant of FIG. 4A implanted on the femoral condyle along with animplant suitable for the tibial plateau, such as that shown in FIG. 2.

FIGS. 5A-N are depictions of another implant suitable for placement onthe femoral condyle. FIG. 5A is a top view of the inferior surface ofthe implant. FIG. 5B is a slightly perspective view of the superiorsurface of the implant. FIG. 5C is a perspective side view of theimplant from a first direction; FIG. 5D is a slightly perspective sideview of the implant from a second direction. FIG. 5E is a side view ofthe implant; FIG. 5F is a view of the superior surface of the implant;FIGS. 5G and H are cross-sectional views of the implant along the linesG and H shown in FIG. 5F. FIG. 5I is an axial view of a femur with theimplant installed on the femoral condyles. FIG. 5J is an anterior viewof the knee joint without the patella wherein the implant is installedon the femoral condyle. FIG. 5K is an anterior view of the knee jointwith an implant of FIG. 5A implanted on the femoral condyles along withan implant suitable for the tibial plateau, such as that shown in FIG.2. FIGS. 5L-M depicts a device implanted within the knee joint. FIG. 5Ndepicts an alternate embodiment of the device which accommodates anpartial removal of the condyle.

FIGS. 6A-G illustrate the device shown in FIG. 5 along with a graphicalrepresentation of the cross-sectional data points comprising the surfacemap.

FIGS. 7A-C depict in implant suitable for use on a patella.

FIGS. 8A-C depict representative side views of a knee joint with any ofthe devices taught installed therein. FIG. 8A depicts the knee with acondyle implant and a patella implant. FIG. 8B depicts an alternate viewof the knee with a condyle implant and a patella implant wherein thecondyle implant covers a greater portion of the surface of the condylein the posterior direction. FIG. 8C illustrates a knee joint wherein theimplant is provided on the condyle, the patella and the tibial plateau.

DETAILED DESCRIPTION OF THE INVENTION

The following description is presented to enable any person skilled inthe art to make and use the invention. Various modifications to theembodiments described will be readily apparent to those skilled in theart, and the generic principles defined herein can be applied to otherembodiments and applications without departing from the spirit and scopeof the present invention as defined by the appended claims. Thus, thepresent invention is not intended to be limited to the embodimentsshown, but is to be accorded the widest scope consistent with theprinciples and features disclosed herein. To the extent necessary toachieve a complete understanding of the invention disclosed, thespecification and drawings of all issued patents, patent publications,and patent applications cited in this application are incorporatedherein by reference.

As will be appreciated by those of skill in the art, methods recitedherein may be carried out in any order of the recited events which islogically possible, as well as the recited order of events. Furthermore,where a range of values is provided, it is understood that everyintervening value, between the upper and lower limit of that range andany other stated or intervening value in that stated range isencompassed within the invention. Also, it is contemplated that anyoptional feature of the inventive variations described may be set forthand claimed independently, or in combination with any one or more of thefeatures described herein.

The practice of the present invention employs, unless otherwiseindicated, conventional methods of x-ray imaging and processing, x-raytomosynthesis, ultrasound including A-scan, B-scan and C-scan, computedtomography (CT scan), magnetic resonance imaging (MRI), opticalcoherence tomography, single photon emission tomography (SPECT) andpositron emission tomography (PET) within the skill of the art. Suchtechniques are explained fully in the literature and need not bedescribed herein. See, e.g., X-Ray Structure Determination: A PracticalGuide, 2nd Edition, editors Stout and Jensen, 1989, John Wiley & Sons,publisher; Body CT: A Practical Approach, editor Slone, 1999,McGraw-Hill publisher; X-ray Diagnosis: A Physician's Approach, editorLam, 1998 Springer-Verlag, publisher; and Dental Radiology:Understanding the X-Ray Image, editor Laetitia Brocklebank 1997, OxfordUniversity Press publisher. See also, The Essential Physics of MedicalImaging (2^(nd) Ed.), Jerrold T. Bushberg, et al.

The present invention provides methods and compositions for repairingjoints, particularly for repairing articular cartilage and forfacilitating the integration of a wide variety of cartilage repairmaterials into a subject. Among other things, the techniques describedherein allow for the customization of cartilage repair material to suita particular subject, for example in terms of size, cartilage thicknessand/or curvature. When the shape (e.g., size, thickness and/orcurvature) of the articular cartilage surface is an exact or nearanatomic fit with the non-damaged cartilage or with the subject'soriginal cartilage, the success of repair is enhanced. The repairmaterial can be shaped prior to implantation and such shaping can bebased, for example, on electronic images that provide informationregarding curvature or thickness of any “normal” cartilage surroundingthe defect and/or on curvature of the bone underlying the defect. Thus,the current invention provides, among other things, for minimallyinvasive methods for partial joint replacement. The methods will requireonly minimal or, in some instances, no loss in bone stock. Additionally,unlike with current techniques, the methods described herein will helpto restore the integrity of the articular surface by achieving an exactor near anatomic match between the implant and the surrounding oradjacent cartilage and/or subchondral bone.

Advantages of the present invention can include, but are not limited to,(i) customization of joint repair, thereby enhancing the efficacy andcomfort level for the patient following the repair procedure; (ii)eliminating the need for a surgeon to measure the defect to be repairedintraoperatively in some embodiments; (iii) eliminating the need for asurgeon to shape the material during the implantation procedure; (iv)providing methods of evaluating curvature of the repair material basedon bone or tissue images or based on intraoperative probing techniques;(v) providing methods of repairing joints with only minimal or, in someinstances, no loss in bone stock; and (vi) improving postoperative jointcongruity.

Thus, the methods described herein allow for the design and use of jointrepair material that more precisely fits the defect (e.g., site ofimplantation) and, accordingly, provides improved repair of the joint.

I. Assessment of Joints and Alignment

The methods and compositions described herein can be used to treatdefects resulting from disease of the cartilage (e.g., osteoarthritis),bone damage, cartilage damage, trauma, and/or degeneration due tooveruse or age. The invention allows, among other things, a healthpractitioner to evaluate and treat such defects. The size, volume andshape of the area of interest can include only the region of cartilagethat has the defect, but preferably will also include contiguous partsof the cartilage surrounding the cartilage defect.

As will be appreciated by those of skill in the art, size, curvatureand/or thickness measurements can be obtained using any suitabletechnique. For example, one-dimensional, two-dimensional, and/orthree-dimensional measurements can be obtained using suitable mechanicalmeans, laser devices, electromagnetic or optical tracking systems,molds, materials applied to the articular surface that harden and“memorize the surface contour,” and/or one or more imaging techniquesknown in the art. Measurements can be obtained non-invasively and/orintraoperatively (e.g., using a probe or other surgical device). As willbe appreciated by those of skill in the art, the thickness of the repairdevice can vary at any given point depending upon the depth of thedamage to the cartilage and/or bone to be corrected at any particularlocation on an articular surface.

FIG. 1A is a flow chart showing steps taken by a practitioner inassessing a joint. First, a practitioner obtains a measurement of atarget joint 10. The step of obtaining a measurement can be accomplishedby taking an image of the joint. This step can be repeated, asnecessary, 11 to obtain a plurality of images in order to further refinethe joint assessment process. Once the practitioner has obtained thenecessary measurements, the information is used to generate a modelrepresentation of the target joint being assessed 30. This modelrepresentation can be in the form of a topographical map or image. Themodel representation of the joint can be in one, two, or threedimensions. It can include a physical model. More than one model can becreated 31, if desired. Either the original model, or a subsequentlycreated model, or both can be used. After the model representation ofthe joint is generated 30, the practitioner can optionally generate aprojected model representation of the target joint in a correctedcondition 40. Again, this step can be repeated 41, as necessary ordesired. Using the difference between the topographical condition of thejoint and the projected image of the joint, the practitioner can thenselect a joint implant 50 that is suitable to achieve the correctedjoint anatomy. As will be appreciated by those of skill in the art, theselection process 50 can be repeated 51 as often as desired to achievethe desired result.

As will be appreciated by those of skill in the art, the practitionercan proceed directly from the step of generating a model representationof the target joint 30 to the step of selecting a suitable jointreplacement implant 50 as shown by the arrow 32. Additionally, followingselection of suitable joint replacement implant 50, the steps ofobtaining measurement of target joint 10, generating modelrepresentation of target joint 30 and generating projected model 40, canbe repeated in series or parallel as shown by the flow 24, 25, 26.

FIG. 1B is an alternate flow chart showing steps taken by a practitionerin assessing a joint. First, a practitioner obtains a measurement of atarget joint 10. The step of obtaining a measurement can be accomplishedby taking an image of the joint. This step can be repeated, asnecessary, 11 to obtain a plurality of images in order to further refinethe joint assessment process. Once the practitioner has obtained thenecessary measurements, the information is used to generate a modelrepresentation of the target joint being assessed 30. This modelrepresentation can be in the form of a topographical map or image. Themodel representation of the joint can be in one, two, or threedimensions. The process can be repeated 31 as necessary or desired. Itcan include a physical model. After the model representation of thejoint is assessed 30, the practitioner can optionally generate aprojected model representation of the target joint in a correctedcondition 40. This step can be repeated 41 as necessary or desired.Using the difference between the topographical condition of the jointand the projected image of the joint, the practitioner can then design ajoint implant 52 that is suitable to achieve the corrected jointanatomy, repeating the design process 53 as often as necessary toachieve the desired implant design. The practitioner can also assesswhether providing additional features, such as lips, pegs, or anchors,will enhance the implants' performance in the target joint.

As will be appreciated by those of skill in the art, the practitionercan proceed directly from the step of generating a model representationof the target joint 30 to the step of designing a suitable jointreplacement implant 52 as shown by the arrow 38. Similar to the flowshown above, following the design of a suitable joint replacementimplant 52, the steps of obtaining measurement of target joint 10,generating model representation of target joint 30 and generatingprojected model 40, can be repeated in series or parallel as shown bythe flow 42, 43, 44.

The joint implant selected or designed achieves anatomic or nearanatomic fit with the existing surface of the joint while presenting amating surface for the opposing joint surface that replicates thenatural joint anatomy. In this instance, both the existing surface ofthe joint can be assessed as well as the desired resulting surface ofthe joint. This technique is particularly useful for implants that arenot anchored into the bone.

As will be appreciated by those of skill in the art, the physician, orother person practicing the invention, can obtain a measurement of atarget joint 10 and then either design 52 or select 50 a suitable jointreplacement implant.

II. Repair Materials

A wide variety of materials find use in the practice of the presentinvention, including, but not limited to, plastics, metals, crystal freemetals, ceramics, biological materials (e.g., collagen or otherextracellular matrix materials), hydroxyapatite, cells (e.g., stemcells, chondrocyte cells or the like), or combinations thereof. Based onthe information (e.g., measurements) obtained regarding the defect andthe articular surface and/or the subchondral bone, a repair material canbe formed or selected. Further, using one or more of these techniquesdescribed herein, a cartilage replacement or regenerating materialhaving a curvature that will fit into a particular cartilage defect,will follow the contour and shape of the articular surface, and willmatch the thickness of the surrounding cartilage. The repair materialcan include any combination of materials, and typically includes atleast one non-pliable material, for example materials that are noteasily bent or changed.

A. Metal and Polymeric Repair Materials

Currently, joint repair systems often employ metal and/or polymericmaterials including, for example, prostheses which are anchored into theunderlying bone (e.g., a femur in the case of a knee prosthesis). See,e.g., U.S. Pat. No. 6,203,576 to Afriat, et al. issued Mar. 20, 2001 andU.S. Pat. No. 6,322,588 to Ogle, et al. issued Nov. 27, 2001, andreferences cited therein. A wide-variety of metals are useful in thepractice of the present invention, and can be selected based on anycriteria. For example, material selection can be based on resiliency toimpart a desired degree of rigidity. Non-limiting examples of suitablemetals include silver, gold, platinum, palladium, iridium, copper, tin,lead, antimony, bismuth, zinc, titanium, cobalt, stainless steel,nickel, iron alloys, cobalt alloys, such as Elgiloy®, acobalt-chromium-nickel alloy, and MP35N, anickel-cobalt-chromium-molybdenum alloy, and Nitinol™, a nickel-titaniumalloy, aluminum, manganese, iron, tantalum, crystal free metals, such asLiquidmetal® alloys (available from LiquidMetal Technologies,www.liquidmetal.com), other metals that can slowly form polyvalent metalions, for example to inhibit calcification of implanted substrates incontact with a patient's bodily fluids or tissues, and combinationsthereof.

Suitable synthetic polymers include, without limitation, polyamides(e.g., nylon), polyesters, polystyrenes, polyacrylates, vinyl polymers(e.g., polyethylene, polytetrafluoroethylene, polypropylene andpolyvinyl chloride), polycarbonates, polyurethanes, poly dimethylsiloxanes, cellulose acetates, polymethyl methacrylates, polyether etherketones, ethylene vinyl acetates, polysulfones, nitrocelluloses, similarcopolymers and mixtures thereof. Bioresorbable synthetic polymers canalso be used such as dextran, hydroxyethyl starch, derivatives ofgelatin, polyvinylpyrrolidone, polyvinyl alcohol,poly[N-(2-hydroxypropyl) methacrylamide], poly(hydroxy acids),poly(epsilon-caprolactone), polylactic acid, polyglycolic acid,poly(dimethyl glycolic acid), poly(hydroxy butyrate), and similarcopolymers can also be used.

Other materials would also be appropriate, for example, the polyketoneknown as polyetheretherketone (PEEK™). This includes the material PEEK450G, which is an unfilled PEEK approved for medical implantationavailable from Victrex of Lancashire, Great Britain. (Victrex is locatedat www.matweb.com or see Boedeker www.boedeker.com). Other sources ofthis material include Gharda located in Panoli, India(www.ghardapolymers.com).

It should be noted that the material selected can also be filled. Forexample, other grades of PEEK are also available and contemplated, suchas 30% glass-filled or 30% carbon filled, provided such materials arecleared for use in implantable devices by the FDA, or other regulatorybody. Glass filled PEEK reduces the expansion rate and increases theflexural modulus of PEEK relative to that portion which is unfilled. Theresulting product is known to be ideal for improved strength, stiffness,or stability. Carbon filled PEEK is known to enhance the compressivestrength and stiffness of PEEK and lower its expansion rate. Carbonfilled PEEK offers wear resistance and load carrying capability.

As will be appreciated, other suitable similarly biocompatiblethermoplastic or thermoplastic polycondensate materials that resistfatigue, have good memory, are flexible, and/or deflectable have verylow moisture absorption, and good wear and/or abrasion resistance, canbe used without departing from the scope of the invention. The implantcan also be comprised of polyetherketoneketone (PEKK).

Other materials that can be used include polyetherketone (PEK),polyetherketoneetherketoneketone (PEKEKK), andpolyetheretherketoneketone (PEEKK), and generally apolyaryletheretherketone. Further other polyketones can be used as wellas other thermoplastics.

Reference to appropriate polymers that can be used for the implant canbe made to the following documents, all of which are incorporated hereinby reference. These documents include: PCT Publication WO 02/02158 A1,dated Jan. 10, 2002 and entitled Bio-Compatible Polymeric Materials; PCTPublication WO 02/00275 A1, dated Jan. 3, 2002 and entitledBio-Compatible Polymeric Materials; and PCT Publication WO 02/00270 A1,dated Jan. 3, 2002 and entitled Bio-Compatible Polymeric Materials.

The polymers can be prepared by any of a variety of approaches includingconventional polymer processing methods. Preferred approaches include,for example, injection molding, which is suitable for the production ofpolymer components with significant structural features, and rapidprototyping approaches, such as reaction injection molding andstereo-lithography. The substrate can be textured or made porous byeither physical abrasion or chemical alteration to facilitateincorporation of the metal coating. Other processes are alsoappropriate, such as extrusion, injection, compression molding and/ormachining techniques. Typically, the polymer is chosen for its physicaland mechanical properties and is suitable for carrying and spreading thephysical load between the joint surfaces.

More than one metal and/or polymer can be used in combination with eachother. For example, one or more metal-containing substrates can becoated with polymers in one or more regions or, alternatively, one ormore polymer-containing substrate can be coated in one or more regionswith one or more metals.

The system or prosthesis can be porous or porous coated. The poroussurface components can be made of various materials including metals,ceramics, and polymers. These surface components can, in turn, besecured by various means to a multitude of structural cores formed ofvarious metals. Suitable porous coatings include, but are not limitedto, metal, ceramic, polymeric (e.g., biologically neutral elastomerssuch as silicone rubber, polyethylene terephthalate and/or combinationsthereof) or combinations thereof. See, e.g., U.S. Pat. No. 3,605,123 toHahn, issued Sep. 20, 1971. U.S. Pat. No. 3,808,606 to Tronzo issued May7, 1974 and U.S. Pat. No. 3,843,975 to Tronzo issued Oct. 29, 1974; U.S.Pat. No. 3,314,420 to Smith issued Apr. 18, 1967; U.S. Pat. No.3,987,499 to Scharbach issued Oct. 26, 1976; and GermanOffenlegungsschrift 2,306,552. There can be more than one coating layerand the layers can have the same or different porosities. See, e.g.,U.S. Pat. No. 3,938,198 to Kahn, et al., issued Feb. 17, 1976.

The coating can be applied by surrounding a core with powdered polymerand heating until cured to form a coating with an internal network ofinterconnected pores. The tortuosity of the pores (e.g., a measure oflength to diameter of the paths through the pores) can be important inevaluating the probable success of such a coating in use on a prostheticdevice. See, also, U.S. Pat. No. 4,213,816 to Morris issued Jul. 22,1980. The porous coating can be applied in the form of a powder and thearticle as a whole subjected to an elevated temperature that bonds thepowder to the substrate. Selection of suitable polymers and/or powdercoatings can be determined in view of the teachings and references citedherein, for example based on the melt index of each.

B. Biological Repair Material

Repair materials can also include one or more biological material eitheralone or in combination with non-biological materials. For example, anybase material can be designed or shaped and suitable cartilagereplacement or regenerating material(s) such as fetal cartilage cellscan be applied to be the base. The cells can be then be grown inconjunction with the base until the thickness (and/or curvature) of thecartilage surrounding the cartilage defect has been reached. Conditionsfor growing cells (e.g., chondrocytes) on various substrates in culture,ex vivo and in vivo are described, for example, in U.S. Pat. No.5,478,739 to Slivka et al. issued Dec. 26, 1995; U.S. Pat. No. 5,842,477to Naughton et al. issued Dec. 1, 1998; U.S. Pat. No. 6,283,980 toVibe-Hansen et al., issued Sep. 4, 2001, and U.S. Pat. No. 6,365,405 toSalzmann et al. issued Apr. 2, 2002. Non-limiting examples of suitablesubstrates include plastic, tissue scaffold, a bone replacement material(e.g., a hydroxyapatite, a bioresorbable material), or any othermaterial suitable for growing a cartilage replacement or regeneratingmaterial on it.

Biological polymers can be naturally occurring or produced in vitro byfermentation and the like. Suitable biological polymers include, withoutlimitation, collagen, elastin, silk, keratin, gelatin, polyamino acids,cat gut sutures, polysaccharides (e.g., cellulose and starch) andmixtures thereof. Biological polymers can be bioresorbable.

Biological materials used in the methods described herein can beautografts (from the same subject); allografts (from another individualof the same species) and/or xenografts (from another species). See,also, International Patent Publications WO 02/22014 to Alexander et al.published Mar. 21, 2002 and WO 97/27885 to Lee published Aug. 7, 1997.In certain embodiments autologous materials are preferred, as they cancarry a reduced risk of immunological complications to the host,including re-absorption of the materials, inflammation and/or scarringof the tissues surrounding the implant site.

In one embodiment of the invention, a probe is used to harvest tissuefrom a donor site and to prepare a recipient site. The donor site can belocated in a xenograft, an allograft or an autograft. The probe is usedto achieve a good anatomic match between the donor tissue sample and therecipient site. The probe is specifically designed to achieve a seamlessor near seamless match between the donor tissue sample and the recipientsite. The probe can, for example, be cylindrical. The distal end of theprobe is typically sharp in order to facilitate tissue penetration.Additionally, the distal end of the probe is typically hollow in orderto accept the tissue. The probe can have an edge at a defined distancefrom its distal end, e.g. at 1 cm distance from the distal end and theedge can be used to achieve a defined depth of tissue penetration forharvesting. The edge can be external or can be inside the hollow portionof the probe. For example, an orthopedic surgeon can take the probe andadvance it with physical pressure into the cartilage, the subchondralbone and the underlying marrow in the case of a joint such as a kneejoint. The surgeon can advance the probe until the external or internaledge reaches the cartilage surface. At that point, the edge will preventfurther tissue penetration thereby achieving a constant and reproducibletissue penetration. The distal end of the probe can include one or moreblades, saw-like structures, or tissue cutting mechanism. For example,the distal end of the probe can include an iris-like mechanismconsisting of several small blades. The blade or blades can be movedusing a manual, motorized or electrical mechanism thereby cuttingthrough the tissue and separating the tissue sample from the underlyingtissue. Typically, this will be repeated in the donor and the recipient.In the case of an iris-shaped blade mechanism, the individual blades canbe moved so as to close the iris thereby separating the tissue samplefrom the donor site.

In another embodiment of the invention, a laser device or aradiofrequency device can be integrated inside the distal end of theprobe. The laser device or the radiofrequency device can be used to cutthrough the tissue and to separate the tissue sample from the underlyingtissue.

In one embodiment of the invention, the same probe can be used in thedonor and in the recipient. In another embodiment, similarly shapedprobes of slightly different physical dimensions can be used. Forexample, the probe used in the recipient can be slightly smaller thanthat used in the donor thereby achieving a tight fit between the tissuesample or tissue transplant and the recipient site. The probe used inthe recipient can also be slightly shorter than that used in the donorthereby correcting for any tissue lost during the separation or cuttingof the tissue sample from the underlying tissue in the donor material.

Any biological repair material can be sterilized to inactivatebiological contaminants such as bacteria, viruses, yeasts, molds,mycoplasmas and parasites. Sterilization can be performed using anysuitable technique, for example radiation, such as gamma radiation.

Any of the biological materials described herein can be harvested withuse of a robotic device. The robotic device can use information from anelectronic image for tissue harvesting.

In certain embodiments, the cartilage replacement material has aparticular biochemical composition. For instance, the biochemicalcomposition of the cartilage surrounding a defect can be assessed bytaking tissue samples and chemical analysis or by imaging techniques.For example, WO 02/22014 to Alexander describes the use of gadoliniumfor imaging of articular cartilage to monitor glycosaminoglycan contentwithin the cartilage. The cartilage replacement or regenerating materialcan then be made or cultured in a manner, to achieve a biochemicalcomposition similar to that of the cartilage surrounding theimplantation site. The culture conditions used to achieve the desiredbiochemical compositions can include, for example, varyingconcentrations. Biochemical composition of the cartilage replacement orregenerating material can, for example, be influenced by controllingconcentrations and exposure times of certain nutrients and growthfactors.

III. Device Design

A. Cartilage Models

Using information on thickness and curvature of the cartilage, aphysical model of the surfaces of the articular cartilage and of theunderlying bone can be created. This physical model can berepresentative of a limited area within the joint or it can encompassthe entire joint. For example, in the knee joint, the physical model canencompass only the medial or lateral femoral condyle, both femoralcondyles and the notch region, the medial tibial plateau, the lateraltibial plateau, the entire tibial plateau, the medial patella, thelateral patella, the entire patella or the entire joint. The location ofa diseased area of cartilage can be determined, for example using a 3Dcoordinate system or a 3D Euclidian distance as described in WO02/22014.

In this way, the size of the defect to be repaired can be determined.This process takes into account that, for example, roughly 80% ofpatients have a healthy lateral component. As will be apparent, some,but not all, defects will include less than the entire cartilage. Thus,in one embodiment of the invention, the thickness of the normal or onlymildly diseased cartilage surrounding one or more cartilage defects ismeasured. This thickness measurement can be obtained at a single pointor, preferably, at multiple points, for example 2 point, 4-6 points,7-10 points, more than 10 points or over the length of the entireremaining cartilage. Furthermore, once the size of the defect isdetermined, an appropriate therapy (e.g., articular repair system) canbe selected such that as much as possible of the healthy, surroundingtissue is preserved.

In other embodiments, the curvature of the articular surface can bemeasured to design and/or shape the repair material. Further, both thethickness of the remaining cartilage and the curvature of the articularsurface can be measured to design and/or shape the repair material.Alternatively, the curvature of the subchondral bone can be measured andthe resultant measurement(s) can be used to either select or shape acartilage replacement material. For example, the contour of thesubchondral bone can be used to re-create a virtual cartilage surface:the margins of an area of diseased cartilage can be identified. Thesubchondral bone shape in the diseased areas can be measured. A virtualcontour can then be created by copying the subchondral bone surface intothe cartilage surface, whereby the copy of the subchondral bone surfaceconnects the margins of the area of diseased cartilage. In shaping thedevice, the contours can be configures to mate with existing cartilageor to account for the removal of some or all of the cartilage.

FIG. 2A shows a slightly perspective view of a joint implant 200 of theinvention suitable for implantation at the tibial plateau of the kneejoint. As shown in FIG. 2A, the implant can be generated using, forexample, a dual surface assessment, as described above with respect toFIGS. 1A and B.

The implant 200 has an upper surface 202, a lower surface 204 and aperipheral edge 206. The upper surface 202 is formed so that it forms amating surface for receiving the opposing joint surface; in thisinstance partially concave to receive the femur. The concave surface canbe variably concave such that it presents a surface to the opposingjoint surface, e.g. the a negative surface of the mating surface of thefemur it communicates with. As will be appreciated by those of skill inthe art, the negative impression, need not be a perfect one.Alternatively, it can be configured to mate with an implant configuredfor the opposing condyle.

The lower surface 204 has a convex surface that matches, or nearlymatches, the tibial plateau of the joint such that it creates ananatomic or near anatomic fit with the tibial plateau. Depending on theshape of the tibial plateau, the lower surface can be partially convexas well. Thus, the lower surface 204 presents a surface to the tibialplateau that fits within the existing surface. It can be formed to matchthe existing surface or to match the surface after articularresurfacing.

As will be appreciated by those of skill in the art, the convex surfaceof the lower surface 204 need not be perfectly convex. Rather, the lowersurface 204 is more likely consist of convex and concave portions thatfit within the existing surface of the tibial plateau or the re-surfacedplateau. Thus, the surface is essentially variably convex and concave.

FIG. 2B shows a top view of the joint implant of FIG. 2A. As shown inFIG. 2B the exterior shape 208 of the implant can be elongated. Theelongated form can take a variety of shapes including elliptical,quasi-elliptical, race-track, etc. However, as will be appreciated theexterior dimension is typically irregular thus not forming a truegeometric shape, e.g. ellipse. As will be appreciated by those of skillin the art, the actual exterior shape of an implant can vary dependingon the nature of the joint defect to be corrected. Thus the ratio of thelength L to the width W can vary from, for example, between 0.25 to 2.0,and more specifically from 0.5 to 1.5. As further shown in FIG. 2B, thelength across an axis of the implant 200 varies when taken at pointsalong the width of the implant. For example, as shown in FIG. 2B,L₁≠L₂≠L₃.

Turning now to FIGS. 2C-E, cross-sections of the implant shown in FIG.2B are depicted along the lines of C-C, D-D, and E-E. The implant has athickness t1, t2 and t3 respectively. As illustrated by thecross-sections, the thickness of the implant varies along both itslength L and width W. The actual thickness at a particular location ofthe implant 200 is a function of the thickness of the cartilage and/orbone to be replaced and the joint mating surface to be replicated.Further, the profile of the implant 200 at any location along its lengthL or width W is a function of the cartilage and/or bone to be replaced.

FIG. 2F is a lateral view of the implant 200 of FIG. 2A. In thisinstance, the height of the implant 200 at a first end h₁ is differentthan the height of the implant at a second end h₂. Further the upperedge 208 can have an overall slope in a downward direction. However, asillustrated the actual slope of the upper edge 208 varies along itslength and can, in some instances, be a positive slope. Further thelower edge 210 can have an overall slope in a downward direction. Asillustrated the actual slope of the lower edge 210 varies along itslength and can, in some instances, be a positive slope. As will beappreciated by those of skill in the art, depending on the anatomy of anindividual patient, an implant can be created wherein h₁ and h₂ areequivalent, or substantially equivalent without departing from the scopeof the invention.

FIG. 2G is a cross-section taken along a sagittal plane in a bodyshowing the implant 200 implanted within a knee joint 1020 such that thelower surface 204 of the implant 200 lies on the tibial plateau 1022 andthe femur 1024 rests on the upper surface 202 of the implant 200. FIG.2H is a cross-section taken along a coronal plane in a body showing theimplant 200 implanted within a knee joint 1020. As is apparent from thisview, the implant 200 is positioned so that it fits within a superiorarticular surface 224. As will be appreciated by those of skill in theart, the articular surface could be the medial or lateral facet, asneeded.

FIG. 2I is a cross-section along an axial plane of the body showing theimplant 200 implanted within a knee joint 1020 showing the view takenfrom an aerial, or upper, view. FIG. 2J is a cross-section of analternate embodiment where the implant is a bit larger such that itextends closer to the bone medially, i.e. towards the edge 1023 of thetibial plateau, as well as extending anteriorly and posteriorly.

FIG. 2K is a cross-section of an implant 200 of the invention accordingto an alternate embodiment. In this embodiment, the lower surface 204further includes a joint anchor 212. As illustrated in this embodiment,the joint anchor 212 forms a protrusion, keel or vertical member thatextends from the lower surface 204 of the implant 200 and projects into,for example, the bone of the joint. Additionally, as shown in FIG. 2Lthe joint anchor 212 can have a cross-member 214 so that from a bottomperspective, the joint anchor 212 has the appearance of a cross or an“x.” As will be appreciated by those of skill in the art, the jointanchor 212 could take on a variety of other forms while stillaccomplishing the same objective of providing increased stability of theimplant 200 in the joint. These forms include, but are not limited to,pins, bulbs, balls, teeth, etc. Additionally, one or more joint anchors212 can be provided as desired. FIGS. 2M and N illustrate cross-sectionsof alternate embodiments of a dual component implant from a side viewand a front view.

In an alternate embodiment shown in FIG. 2M it may be desirable toprovide a one or more cross-members 220 on the lower surface 204 inorder to provide a bit of translation movement of the implant relativeto the surface of the femur, or femur implant. In that event, thecross-member can be formed integral to the surface of the implant or canbe separate pieces that fit within a groove 222 on the lower surface 204of the implant 200. The groove can form a single channel as shown inFIG. 2N1, or can have more than one channel as shown in FIG. 2N2. Ineither event, the cross-bar then fits within the channel as shown inFIGS. 2N1-N2. The cross-bar members 220 can form a solid or hollow tubeor pipe structure as shown in FIG. 2P. Where two, or more, tubes 220communicate to provide translation, a groove 221 can be provided alongthe surface of one or both cross-members to interlock the tubes into across-bar member further stabilizing the motion of the cross-barrelative to the implant 200. As will be appreciated by those of skill inthe art, the cross-bar member 220 can be formed integrally with theimplant without departing from the scope of the invention.

As shown in FIGS. 2Q-R, it is anticipated that the surface of the tibialplateau will be prepared by forming channels thereon to receive thecross-bar members. Thus facilitating the ability of the implant to seatsecurely within the joint while still providing movement about an axiswhen the knee joint is in motion.

Turning now to FIGS. 3A-I an implant suitable for providing an opposingjoint surface to the implant of FIG. 2A is shown. This implant correctsa defect on an inferior surface of the femur 1024 (e.g., the condyle ofthe femur that mates with the tibial plateau) and can be used alone,i.e., on the femur 1024, or in combination with another joint repairdevice.

FIG. 3A shows a perspective view of the implant 300 having a curvedmating surface 302 and convex joint abutting surface 304. The jointabutting surface 304 need not form an anatomic or near anatomic fit withthe femur in view of the anchors 306 provided to facilitate connectionof the implant to the bone. In this instance, the anchors 306 are shownas pegs having notched heads. The notches facilitate the anchoringprocess within the bone. However, pegs without notches can be used aswell as pegs with other configurations that facilitate the anchoringprocess. Pegs and other portions of the implant can be porous coated.The implant can be inserted without bone cement or with use of bonecement. The implant can be designed to abut the subchondral bone, i.e.it can substantially follow the contour of the subchondral bone. Thishas the advantage that no bone needs to be removed other than for theplacement of the peg holes thereby significantly preserving bone stock.

The anchors 306 could take on a variety of other forms without departingfrom the scope of the invention while still accomplishing the sameobjective of providing increased stability of the implant 300 in thejoint. These forms include, but are not limited to, pins, bulbs, balls,teeth, etc. Additionally, one or more joint anchors 306 can be providedas desired. As illustrated in FIG. 3, three pins are used to anchor theimplant 300. However, more or fewer joint anchors, or pins, can be usedwithout departing from the scope of the invention.

FIG. 3B shows a slightly perspective superior view of the bone matingsurface 304 further illustrating the use of three anchors 306 to anchorthe implant to the bone. Each anchor 306 has a stem 310 with a head 312on top. As shown in FIG. 3C, the stem 310 has parallel walls such thatit forms a tube or cylinder that extends from the bone mating surface304. A section of the stem forms a narrowed neck 314 proximal to thehead 312. As will be appreciated by those of skill in the art, the wallsneed not be parallel, but rather can be sloped to be shaped like a cone.Additionally, the neck 314 need not be present, nor the head 312. Asdiscussed above, other configurations suitable for anchoring can be usedwithout departing from the scope of the invention.

Turning now to FIG. 3D, a view of the tibial plateau mating surface 302of the implant 300 is illustrated. As is apparent from this view, thesurface is curved such that it is convex or substantially convex inorder to mate with the concave surface of the plateau. FIG. 3Eillustrates the upper surface 304 of the implant 300 furtherillustrating the use of three pegs 306 for anchoring the implant 300 tothe bone. As illustrated, the three pegs 306 are positioned to form atriangle. However, as will be appreciated by those of skill in the art,one or more pegs can be used, and the orientation of the pegs 306 to oneanother can be as shown, or any other suitable orientation that enablesthe desired anchoring. FIG. 3F illustrated a cross section of theimplant 300 taken along the lines F-F shown in FIG. 3E.

FIG. 3G illustrates the axial view of the femur 1000 having a lateralcondyle 1002 and a medial condyle 1004. The intercondylar fossa is alsoshown 1006 along with the lateral epicondyle 1008 and medial epicondyle1010. Also shown is the patellar surface of the femur 1012. The implant300 illustrated in FIG. 3A, is illustrated covering a portion of thelateral condyle. The pegs 306 are also shown that facilitate anchoringthe implant 300 to the condyle.

FIG. 3H illustrates a knee joint 1020 from an anterior perspective. Theimplant 300 is implanted over the lateral condyle. As shown in FIG. 3Ithe implant 300 is positioned such that it communicates with an implant200 designed to correct a defect in the tibial plateau, such as thoseshown in FIG. 2.

FIGS. 4A and 4B illustrate another implant 400. As shown in FIG. 4A, theimplant 400 is configured such that it covers both the lateral andmedial femoral condyle along with the patellar surface of the femur1012. The implant 400 has a lateral condyle component 410 and a medialcondyle component 420 and a bridge 430 that connects the lateral condylecomponent 410 to the medial condyle component 420 while covering atleast a portion of the patellar surface of the femur 1012. The implant400 can optionally oppose one or more of the implants, such as thoseshown in FIG. 2. FIG. 4B is a side view of the implant of FIG. 4A. Asshown in FIG. 4B, the superior surface 402 of the implant 400 is curvedto correspond to the curvature of the femoral condyles. The curvaturecan be configured such that it corresponds to the actual curvature ofone or both of the existing femoral condyles, or to the curvature of oneor both of the femoral condyles after resurfacing of the joint. One ormore pegs 430 can be provided to assist in anchoring the implant to thebone.

FIG. 4C illustrates a top view of the implant 400 shown in FIG. 4A. Asis should be appreciated from this view, the inferior surface 404 of theimplant 400 is configured to conform to the shape of the femoralcondyles, e.g. the shape healthy femoral condyles would present to thetibial surface in a non-damaged joint.

FIGS. 4D and E illustrate perspective views of the implant from theinferior surface (i.e., tibial plateau mating surface).

FIG. 4F illustrates the axial view of the femur 1000 having a lateralcondyle 1002 and a medial condyle 1004. The intercondylar fossa is alsoshown 1006 along with the lateral epicondyle 1008. The implant 400illustrated in FIG. 4A, is illustrated covering both condyles and thepatellar surface of the femur 1012. The pegs 430 are also shown thatfacilitate anchoring the implant 400 to the condyle.

FIG. 4G illustrates a knee joint 1050 from an anterior perspective. Theimplant 400 is implanted over both condyles. As shown in FIG. 4H theimplant 400 is positioned such that it communicates with an implant 200designed to correct a defect in the tibial plateau, such as those shownin FIG. 2.

As will be appreciated by those of skill in the art, the implant 400 canbe manufactured from a material that has memory such that the implantcan be configured to snap-fit over the condyle. Alternatively, it can beshaped such that it conforms to the surface without the need of asnap-fit.

FIGS. 5A and 5B illustrate yet another implant 500 suitable forrepairing a damaged condyle. As shown in FIG. 5A, the implant 500 isconfigured such that it covers only one of the lateral or medial femoralcondyles 510. The implant differs from the implant of FIG. 3 in that theimplant 500 also covers at least a portion of the patellar surface ofthe femur 512.

The implant can optionally oppose one or more of the implants, such asthose shown in FIG. 2 and can be combined with other implants, such asthe implants of FIG. 3. FIG. 5C is a perspective side view of theimplant of FIG. 5A. As shown in FIG. 5C, the superior surface 502 of theimplant 500 is curved to correspond to the curvature of the femoralcondyle that it mates with and the portion of the patellar surface ofthe femur that it covers. One or more pegs 530 can be provided to assistin anchoring the implant to the bone.

FIG. 5D illustrates a perspective top view of the implant 500 shown inFIG. 5A. As is should be appreciated from this view, the inferiorsurface 504 of the implant 500 is configured to conform to the projectedshape of the femoral condyles, e.g. the shape healthy femoral condyleswould present to the tibial surface in a non-damaged joint.

FIG. 5E is a side view of the implant 500 illustrating the pegs 530extending from the superior surface. FIG. 5F illustrates the superiorsurface of the implant 500 with the pegs 530 extending from the superiorsurface. FIGS. 5G and H illustrate cross-sections along the lines G-Gand H-H shown in FIG. 5F.

FIG. 5I illustrates the axial view of the femur 1000 having a lateralcondyle 1002 and a medial condyle 1004. The intercondylar fossa is alsoshown 1006 along with the lateral epicondyle 1008 and the medialepicondyle 1010. The patellar surface of the femur 1012 is alsoillustrated. The implant 500, illustrated in FIG. 5A, is shown coveringthe lateral condyle and a portion of the patellar surface of the femur1012. The pegs 530 are also shown that facilitate anchoring the implant500 to the condyle and patellar surface.

FIG. 5J illustrates a knee joint 1020 from an anterior perspective. Theimplant 500 is implanted over the lateral condyle. FIG. 5K illustrates aknee joint 1020 with the implant 500 covering the medial condyle 1004.As illustrated in FIGS. 5K and K the shape of the implant 500corresponding to the patella surface can take on a variety of curvatureswithout departing from the scope of the invention.

Turning now to FIGS. 5L and M the implant 500 is positioned such that itcommunicates with an implant 200 designed to correct a defect in thetibial plateau, such as those shown in FIG. 2.

In another embodiment of the invention, the implant 500 can have asuperior surface 502 which substantially conforms to the surface of thecondyle but which has at one flat portion corresponding to an obliquecut on the bone as shown in FIG. 5N.

FIGS. 6A-G illustrate the implant 500 of FIG. 5 with a graphicalrepresentation of the cross-sections 610, 620 from which a surface shapeof the implant is derived. FIG. 6A illustrates a top view of the implant500 sitting on top of the extracted surface shape 600. This view of theimplant 500 illustrates a notch 514 associated with the bridge sectionof the implant 512 which covers the patellar surface of the femur (orthe trochlea region) to provide a mating surface that approximates thecartilage surface. As will be appreciated by those of skill in the art,the shape of an implant designed for the medial condyle would notnecessarily be a mirror image of the implant designed for the lateralcondyle because of differences in anatomy. Thus, for example, the notch514 would not be present in an implant designed for the medial condyleand the patellar surface of the femur.

FIG. 6B illustrates a bottom view of the implant 500 layered overanother derived surface shape 601. FIG. 6C is a bottom view showing theimplant 500 extending through the extracted surface shape 600 shown inFIG. 6A. FIG. 6D is a close-up view of the FIG. 6C showing the condylarwing of the implant covering the extracted surface 600. FIG. 6Eillustrates a top posterior view of the implant 500 positioned over thegraphical representation of the surface shape 600. FIG. 6F is ananterior view and FIG. 6G is a bottom-posterior view.

FIGS. 7A-C illustrate a variety of patellar implants 700 having one ormore pegs 710 as shown in FIGS. 7B-C. As will be appreciated by those ofskill in the art, other designs can be arrived at using the teachings ofthis disclosure without departing from the scope of the invention.

FIGS. 8A-C illustrate a lateral view of a knee 1020 having a combinationof the implants of implanted thereof. In FIG. 8A, an implant coveringthe condyle 800, is illustrated. Suitable implants can be, for example,those shown in FIGS. 3-6, as will be appreciated the portion of thecondyle covered anterior to posterior can include the entire weightbearing surface, a portion thereof, or a surface greater than the weightbearing surface. Thus, for example, the implant can be configured toterminate prior to the sulcus terminalis or after the sulcus terminalis(e.g., the groove on the femur that coincides with the area where loadbearing stops). As shown in FIGS. 8A-B, a patellar implant 700 can alsobe provided. FIG. 8C illustrates a knee having a condyle implant 800, apatellar implant 700 and an implant for the tibial plateau 200.

The arthroplasty system can be designed to reflect aspects of the tibialshape, femoral shape and/or patellar shape. Tibial shape and femoralshape can include cartilage, bone or both. Moreover, the shape of theimplant can also include portions or all components of other articularstructures such as the menisci. The menisci are compressible, inparticular during gait or loading. For this reason, the implant can bedesigned to incorporate aspects of the meniscal shape accounting forcompression of the menisci during loading or physical activities. Forexample, the undersurface 204 of the implant 200 can be designed tomatch the shape of the tibial plateau including cartilage or bone orboth. The superior surface 202 of the implant 200 can be a composite ofthe articular surface of the tibia (in particular in areas that are notcovered by menisci) and the meniscus. Thus, the outer aspects of thedevice can be a reflection of meniscal height. Accounting forcompression, this can be, for example, 20%, 40%, 60% or 80% ofuncompressed meniscal height.

Similarly the superior surface 304 of the implant 300 can be designed tomatch the shape of the femoral condyle including cartilage or bone orboth. The inferior surface 302 of the implant 300 can be a composite ofthe surface of the tibial plateau (in particular in areas that are notcovered by menisci) and the meniscus. Thus, at least a portion of theouter aspects of the device can be a reflection of meniscal height.Accounting for compression, this can be, for example, 20%, 40%, 60% or80% of uncompressed meniscal height. These same properties can beapplied to the implants shown in FIGS. 4-6, as well.

In some embodiments, the outer aspect of the device reflecting themeniscal shape can be made of another, preferably compressible material.If a compressible material is selected it is preferably designed tosubstantially match the compressibility and biomechanical behavior ofthe meniscus. The entire device can be made of such a material ornon-metallic materials in general.

The height and shape of the menisci for any joint surface to be repairedcan be measured directly on an imaging test. If portions, or all, of themeniscus are torn, the meniscal height and shape can be derived frommeasurements of a contralateral joint or using measurements of otherarticular structures that can provide an estimate on meniscaldimensions.

In another embodiment, the superior face of the implants 300, 400 or 500can be shaped according to the femur. The shape can preferably bederived from the movement patterns of the femur relative to the tibialplateau thereby accounting for variations in femoral shape andtibiofemoral contact area as the femoral condyle flexes, extends,rotates, translates and glides on the tibia and menisci.

The movement patterns can be measured using any current or future testknow in the art such as fluoroscopy, MRI, gait analysis and combinationsthereof.

The arthroplasty can have two or more components, one essentially matingwith the tibial surface and the other substantially articulating withthe femoral component. The two components can have a flat opposingsurface. Alternatively, the opposing surface can be curved. Thecurvature can be a reflection of the tibial shape, the femoral shapeincluding during joint motion, and the meniscal shape and combinationsthereof.

Examples of single-component systems include, but are not limited to, aplastic, a polymer, a metal, a metal alloy, crystal free metals, abiologic material or combinations thereof. In certain embodiments, thesurface of the repair system facing the underlying bone can be smooth.In other embodiments, the surface of the repair system facing theunderlying bone can be porous or porous-coated. In another aspect, thesurface of the repair system facing the underlying bone is designed withone or more grooves, for example to facilitate the in-growth of thesurrounding tissue. The external surface of the device can have astep-like design, which can be advantageous for altering biomechanicalstresses. Optionally, flanges can also be added at one or more positionson the device (e.g., to prevent the repair system from rotating, tocontrol toggle and/or prevent settling into the marrow cavity). Theflanges can be part of a conical or a cylindrical design. A portion orall of the repair system facing the underlying bone can also be flatwhich can help to control depth of the implant and to prevent toggle.

Non-limiting examples of multiple-component systems include combinationsof metal, plastic, metal alloys, crystal free metals, and one or morebiological materials. One or more components of the articular surfacerepair system can be composed of a biologic material (e.g. a tissuescaffold with cells such as cartilage cells or stem cells alone orseeded within a substrate such as a bioresorable material or a tissuescaffold, allograft, autograft or combinations thereof) and/or anon-biological material (e.g., polyethylene or a chromium alloy such aschromium cobalt).

Thus, the repair system can include one or more areas of a singlematerial or a combination of materials, for example, the articularsurface repair system can have a first and a second component. The firstcomponent is typically designed to have size, thickness and curvaturesimilar to that of the cartilage tissue lost while the second componentis typically designed to have a curvature similar to the subchondralbone. In addition, the first component can have biomechanical propertiessimilar to articular cartilage, including but not limited to similarelasticity and resistance to axial loading or shear forces. The firstand the second component can consist of two different metals or metalalloys. One or more components of the system (e.g., the second portion)can be composed of a biologic material including, but not limited tobone, or a non-biologic material including, but not limited tohydroxyapatite, tantalum, a chromium alloy, chromium cobalt or othermetal alloys.

One or more regions of the articular surface repair system (e.g., theouter margin of the first portion and/or the second portion) can bebioresorbable, for example to allow the interface between the articularsurface repair system and the patient's normal cartilage, over time, tobe filled in with hyaline or fibrocartilage. Similarly, one or moreregions (e.g., the outer margin of the first portion of the articularsurface repair system and/or the second portion) can be porous. Thedegree of porosity can change throughout the porous region, linearly ornon-linearly, for where the degree of porosity will typically decreasetowards the center of the articular surface repair system. The pores canbe designed for in-growth of cartilage cells, cartilage matrix, andconnective tissue thereby achieving a smooth interface between thearticular surface repair system and the surrounding cartilage.

The repair system (e.g., the second component in multiple componentsystems) can be attached to the patient's bone with use of a cement-likematerial such as methylmethacrylate, injectable hydroxy- orcalcium-apatite materials and the like.

In certain embodiments, one or more portions of the articular surfacerepair system can be pliable or liquid or deformable at the time ofimplantation and can harden later. Hardening can occur, for example,within 1 second to 2 hours (or any time period therebetween), preferablywith in 1 second to 30 minutes (or any time period therebetween), morepreferably between 1 second and 10 minutes (or any time periodtherebetween).

One or more components of the articular surface repair system can beadapted to receive injections. For example, the external surface of thearticular surface repair system can have one or more openings therein.The openings can be sized to receive screws, tubing, needles or otherdevices which can be inserted and advanced to the desired depth, forexample, through the articular surface repair system into the marrowspace. Injectables such as methylmethacrylate and injectable hydroxy- orcalcium-apatite materials can then be introduced through the opening (ortubing inserted therethrough) into the marrow space thereby bonding thearticular surface repair system with the marrow space. Similarly, screwsor pins, or other anchoring mechanisms can be inserted into the openingsand advanced to the underlying subchondral bone and the bone marrow orepiphysis to achieve fixation of the articular surface repair system tothe bone. Portions or all components of the screw or pin can bebioresorbable, for example, the distal portion of a screw that protrudesinto the marrow space can be bioresorbable. During the initial periodafter the surgery, the screw can provide the primary fixation of thearticular surface repair system. Subsequently, ingrowth of bone into aporous coated area along the undersurface of the articular cartilagerepair system can take over as the primary stabilizer of the articularsurface repair system against the bone.

The articular surface repair system can be anchored to the patient'sbone with use of a pin or screw or other attachment mechanism. Theattachment mechanism can be bioresorbable. The screw or pin orattachment mechanism can be inserted and advanced towards the articularsurface repair system from a non-cartilage covered portion of the boneor from a non-weight-bearing surface of the joint.

The interface between the articular surface repair system and thesurrounding normal cartilage can be at an angle, for example oriented atan angle of 90 degrees relative to the underlying subchondral bone.Suitable angles can be determined in view of the teachings herein, andin certain cases, non-90 degree angles can have advantages with regardto load distribution along the interface between the articular surfacerepair system and the surrounding normal cartilage.

The interface between the articular surface repair system and thesurrounding normal cartilage and/or bone can be covered with apharmaceutical or bioactive agent, for example a material thatstimulates the biological integration of the repair system into thenormal cartilage and/or bone. The surface area of the interface can beirregular, for example, to increase exposure of the interface topharmaceutical or bioactive agents.

E. Pre-Existing Repair Systems

As described herein, repair systems of various sizes, curvatures andthicknesses can be obtained. These repair systems can be catalogued andstored to create a library of systems from which an appropriate systemfor an individual patient can then be selected. In other words, adefect, or an articular surface, is assessed in a particular subject anda pre-existing repair system having a suitable shape and size isselected from the library for further manipulation (e.g., shaping) andimplantation.

F. Mini-Prosthesis

As noted above, the methods and compositions described herein can beused to replace only a portion of the articular surface, for example, anarea of diseased cartilage or lost cartilage on the articular surface.In these systems, the articular surface repair system can be designed toreplace only the area of diseased or lost cartilage or it can extendbeyond the area of diseased or lost cartilage, e.g., 3 or 5 mm intonormal adjacent cartilage. In certain embodiments, the prosthesisreplaces less than about 70% to 80% (or any value therebetween) of thearticular surface (e.g., any given articular surface such as a singlefemoral condyle, etc.), preferably, less than about 50% to 70% (or anyvalue therebetween), more preferably, less than about 30% to 50% (or anyvalue therebetween), more preferably less than about 20% to 30% (or anyvalue therebetween), even more preferably less than about 20% of thearticular surface.

The prosthesis can include multiple components, for example a componentthat is implanted into the bone (e.g., a metallic device) attached to acomponent that is shaped to cover the defect of the cartilage overlayingthe bone. Additional components, for example intermediate plates,meniscal repair systems and the like can also be included. It iscontemplated that each component replaces less than all of thecorresponding articular surface. However, each component need notreplace the same portion of the articular surface. In other words, theprosthesis can have a bone-implanted component that replaces less than30% of the bone and a cartilage component that replaces 60% of thecartilage. The prosthesis can include any combination, provided eachcomponent replaces less than the entire articular surface.

The articular surface repair system can be formed or selected so that itwill achieve a near anatomic fit or match with the surrounding oradjacent cartilage or bone. Typically, the articular surface repairsystem is formed and/or selected so that its outer margin located at theexternal surface will be aligned with the surrounding or adjacentcartilage.

Thus, the articular repair system can be designed to replace theweight-bearing portion (or more or less than the weight bearing portion)of an articular surface, for example in a femoral condyle. Theweight-bearing surface refers to the contact area between two opposingarticular surfaces during activities of normal daily living (e.g.,normal gait). At least one or more weight-bearing portions can bereplaced in this manner, e.g., on a femoral condyle and on a tibia.

In other embodiments, an area of diseased cartilage or cartilage losscan be identified in a weight-bearing area and only a portion of theweight-bearing area, specifically the portion containing the diseasedcartilage or area of cartilage loss, can be replaced with an articularsurface repair system.

In another embodiment, the articular repair system can be designed orselected to replace substantially all of the articular surface, e.g. acondyle.

In another embodiment, for example, in patients with diffuse cartilageloss, the articular repair system can be designed to replace an areaslightly larger than the weight-bearing surface.

In certain aspects, the defect to be repaired is located only on onearticular surface, typically the most diseased surface. For example, ina patient with severe cartilage loss in the medial femoral condyle butless severe disease in the tibia, the articular surface repair systemcan only be applied to the medial femoral condyle. Preferably, in anymethods described herein, the articular surface repair system isdesigned to achieve an exact or a near anatomic fit with the adjacentnormal cartilage.

In other embodiments, more than one articular surface can be repaired.The area(s) of repair will be typically limited to areas of diseasedcartilage or cartilage loss or areas slightly greater than the area ofdiseased cartilage or cartilage loss within the weight-bearingsurface(s).

In another embodiment, one or more components of the articular surfacerepair (e.g., the surface of the system that is pointing towards theunderlying bone or bone marrow) can be porous or porous coated. Avariety of different porous metal coatings have been proposed forenhancing fixation of a metallic prosthesis by bone tissue in-growth.Thus, for example, U.S. Pat. No. 3,855,638 to Pilliar issued Dec. 24,2974, discloses a surgical prosthetic device, which can be used as abone prosthesis, comprising a composite structure consisting of a solidmetallic material substrate and a porous coating of the same solidmetallic material adhered to and extending over at least a portion ofthe surface of the substrate. The porous coating consists of a pluralityof small discrete particles of metallic material bonded together attheir points of contact with each other to define a plurality ofconnected interstitial pores in the coating. The size and spacing of theparticles, which can be distributed in a plurality of monolayers, can besuch that the average interstitial pore size is not more than about 200microns. Additionally, the pore size distribution can be substantiallyuniform from the substrate-coating interface to the surface of thecoating. In another embodiment, the articular surface repair system cancontain one or more polymeric materials that can be loaded with andrelease therapeutic agents including drugs or other pharmacologicaltreatments that can be used for drug delivery. The polymeric materialscan, for example, be placed inside areas of porous coating. Thepolymeric materials can be used to release therapeutic drugs, e.g. boneor cartilage growth stimulating drugs. This embodiment can be combinedwith other embodiments, wherein portions of the articular surface repairsystem can be bioresorbable. For example, the first layer of anarticular surface repair system or portions of its first layer can bebioresorbable. As the first layer gets increasingly resorbed, localrelease of a cartilage growth-stimulating drug can facilitate in-growthof cartilage cells and matrix formation.

In any of the methods or compositions described herein, the articularsurface repair system can be pre-manufactured with a range of sizes,curvatures and thicknesses. Alternatively, the articular surface repairsystem can be custom-made for an individual patient.

IV. Manufacturing

A. Shaping

In certain instances shaping of the repair material will be requiredbefore or after formation (e.g., growth to desired thickness), forexample where the thickness of the required cartilage material is notuniform (e.g., where different sections of the cartilage replacement orregenerating material require different thicknesses).

The replacement material can be shaped by any suitable techniqueincluding, but not limited to, mechanical abrasion, laser abrasion orablation, radiofrequency treatment, cryoablation, variations in exposuretime and concentration of nutrients, enzymes or growth factors and anyother means suitable for influencing or changing cartilage thickness.See, e.g., WO 00/15153 to Mansmann published Mar. 23, 2000; If enzymaticdigestion is used, certain sections of the cartilage replacement orregenerating material can be exposed to higher doses of the enzyme orcan be exposed longer as a means of achieving different thicknesses andcurvatures of the cartilage replacement or regenerating material indifferent sections of said material.

The material can be shaped manually and/or automatically, for exampleusing a device into which a pre-selected thickness and/or curvature hasbeen input and then programming the device using the input informationto achieve the desired shape.

In addition to, or instead of, shaping the cartilage repair material,the site of implantation (e.g., bone surface, any cartilage materialremaining, etc.) can also be shaped by any suitable technique in orderto enhance integration of the repair material.

B. Sizing

The articular repair system can be formed or selected so that it willachieve a near anatomic fit or match with the surrounding or adjacentcartilage, subchondral bone, menisci and/or other tissue. The shape ofthe repair system can be based on the analysis of an electronic image(e.g. MRI, CT, digital tomosynthesis, optical coherence tomography orthe like). If the articular repair system is intended to replace an areaof diseased cartilage or lost cartilage, the near anatomic fit can beachieved using a method that provides a virtual reconstruction of theshape of healthy cartilage in an electronic image.

In one embodiment of the invention, a near normal cartilage surface atthe position of the cartilage defect can be reconstructed byinterpolating the healthy cartilage surface across the cartilage defector area of diseased cartilage. This can, for example, be achieved bydescribing the healthy cartilage by means of a parametric surface (e.g.a B-spline surface), for which the control points are placed such thatthe parametric surface follows the contour of the healthy cartilage andbridges the cartilage defect or area of diseased cartilage. Thecontinuity properties of the parametric surface will provide a smoothintegration of the part that bridges the cartilage defect or area ofdiseased cartilage with the contour of the surrounding healthycartilage. The part of the parametric surface over the area of thecartilage defect or area of diseased cartilage can be used to determinethe shape or part of the shape of the articular repair system to matchwith the surrounding cartilage.

In another embodiment, a near normal cartilage surface at the positionof the cartilage defect or area of diseased cartilage can bereconstructed using morphological image processing. In a first step, thecartilage can be extracted from the electronic image using manual,semi-automated and/or automated segmentation techniques (e.g., manualtracing, region growing, live wire, model-based segmentation), resultingin a binary image. Defects in the cartilage appear as indentations thatcan be filled with a morphological closing operation performed in 2-D or3-D with an appropriately selected structuring element. The closingoperation is typically defined as a dilation followed by an erosion. Adilation operator sets the current pixel in the output image to 1 if atleast one pixel of the structuring element lies inside a region in thesource image. An erosion operator sets the current pixel in the outputimage to 1 if the whole structuring element lies inside a region in thesource image. The filling of the cartilage defect or area of diseasedcartilage creates a new surface over the area of the cartilage defect orarea of diseased cartilage that can be used to determine the shape orpart of the shape of the articular repair system to match with thesurrounding cartilage or subchondral bone.

As described above, the articular repair system can be formed orselected from a library or database of systems of various sizes,curvatures and thicknesses so that it will achieve a near anatomic fitor match with the surrounding or adjacent cartilage and/or subchondralbone. These systems can be pre-made or made to order for an individualpatient. In order to control the fit or match of the articular repairsystem with the surrounding or adjacent cartilage or subchondral bone ormenisci and other tissues preoperatively, a software program can be usedthat projects the articular repair system over the anatomic positionwhere it will be implanted. Suitable software is commercially availableand/or readily modified or designed by a skilled programmer.

In yet another embodiment, the articular surface repair system can beprojected over the implantation site using one or more 3-D images. Thecartilage and/or subchondral bone and other anatomic structures areextracted from a 3-D electronic image such as an MRI or a CT usingmanual, semi-automated and/or automated segmentation techniques. A 3-Drepresentation of the cartilage and/or subchondral bone and otheranatomic structures as well as the articular repair system is generated,for example using a polygon or NURBS surface or other parametric surfacerepresentation. For a description of various parametric surfacerepresentations see, for example Foley, J. D. et al., Computer Graphics:Principles and Practice in C; Addison-Wesley, 2^(nd) edition, 1995).

The 3-D representations of the cartilage and/or subchondral bone andother anatomic structures and the articular repair system can be mergedinto a common coordinate system. The articular repair system can then beplaced at the desired implantation site. The representations of thecartilage, subchondral bone, menisci and other anatomic structures andthe articular repair system are rendered into a 3-D image, for exampleapplication programming interfaces (APIs) OpenGL® (standard library ofadvanced 3-D graphics functions developed by SGI, Inc.; available aspart of the drivers for PC-based video cards, for example fromwww.nvidia.com for NVIDIA video cards or www.3dlabs.com for 3Dlabsproducts, or as part of the system software for Unix workstations) orDirectX® (multimedia API for Microsoft Windows® based PC systems;available from www.microsoft.com). The 3-D image can be rendered showingthe cartilage, subchondral bone, menisci or other anatomic objects, andthe articular repair system from varying angles, e.g. by rotating ormoving them interactively or non-interactively, in real-time ornon-real-time.

The software can be designed so that the articular repair system,including surgical tools and instruments with the best fit relative tothe cartilage and/or subchondral bone is automatically selected, forexample using some of the techniques described above. Alternatively, theoperator can select an articular repair system, including surgical toolsand instruments and project it or drag it onto the implantation siteusing suitable tools and techniques. The operator can move and rotatethe articular repair systems in three dimensions relative to theimplantation site and can perform a visual inspection of the fit betweenthe articular repair system and the implantation site. The visualinspection can be computer assisted. The procedure can be repeated untila satisfactory fit has been achieved. The procedure can be performedmanually by the operator; or it can be computer-assisted in whole orpart. For example, the software can select a first trial implant thatthe operator can test. The operator can evaluate the fit. The softwarecan be designed and used to highlight areas of poor alignment betweenthe implant and the surrounding cartilage or subchondral bone or meniscior other tissues. Based on this information, the software or theoperator can then select another implant and test its alignment. One ofskill in the art will readily be able to select, modify and/or createsuitable computer programs for the purposes described herein.

In another embodiment, the implantation site can be visualized using oneor more cross-sectional 2-D images. Typically, a series of 2-Dcross-sectional images will be used. The 2-D images can be generatedwith imaging tests such as CT, MRI, digital tomosynthesis, ultrasound,or optical coherence tomography using methods and tools known to thoseof skill in the art. The articular repair system can then besuperimposed onto one or more of these 2-D images. The 2-Dcross-sectional images can be reconstructed in other planes, e.g. fromsagittal to coronal, etc. Isotropic data sets (e.g., data sets where theslice thickness is the same or nearly the same as the in-planeresolution) or near isotropic data sets can also be used. Multipleplanes can be displayed simultaneously, for example using a split screendisplay. The operator can also scroll through the 2-D images in anydesired orientation in real time or near real time; the operator canrotate the imaged tissue volume while doing this. The articular repairsystem can be displayed in cross-section utilizing different displayplanes, e.g. sagittal, coronal or axial, typically matching those of the2-D images demonstrating the cartilage, subchondral bone, menisci orother tissue. Alternatively, a three-dimensional display can be used forthe articular repair system. The 2-D electronic image and the 2-D or 3-Drepresentation of the articular repair system can be merged into acommon coordinate system. The articular repair system can then be placedat the desired implantation site. The series of 2-D cross-sections ofthe anatomic structures, the implantation site and the articular repairsystem can be displayed interactively (e.g. the operator can scrollthrough a series of slices) or non-interactively (e.g. as an animationthat moves through the series of slices), in real-time or non-real-time.

C. Rapid Prototyping

Rapid protoyping is a technique for fabricating a three-dimensionalobject from a computer model of the object. A special printer is used tofabricate the prototype from a plurality of two-dimensional layers.Computer software sections the representations of the object into aplurality of distinct two-dimensional layers and then athree-dimensional printer fabricates a layer of material for each layersectioned by the software. Together the various fabricated layers formthe desired prototype. More information about rapid prototypingtechniques is available in US Patent Publication No 2002/0079601 A1 toRussell et al., published Jun. 27, 2002. An advantage to using rapidprototyping is that it enables the use of free form fabricationtechniques that use toxic or potent compounds safely. These compoundscan be safely incorporated in an excipient envelope, which reducesworker exposure.

A powder piston and build bed are provided. Powder includes any material(metal, plastic, etc.) that can be made into a powder or bonded with aliquid. The power is rolled from a feeder source with a spreader onto asurface of a bed. The thickness of the layer is controlled by thecomputer. The print head then deposits a binder fluid onto the powderlayer at a location where it is desired that the powder bind. Powder isagain rolled into the build bed and the process is repeated, with thebinding fluid deposition being controlled at each layer to correspond tothe three-dimensional location of the device formation. For a furtherdiscussion of this process see, for example, US Patent Publication No2003/017365A1 to Monkhouse et al. published Sep. 18, 2003.

The rapid prototyping can use the two dimensional images obtained, asdescribed above in Section I, to determine each of the two-dimensionalshapes for each of the layers of the prototyping machine. In thisscenario, each two dimensional image slice would correspond to a twodimensional prototype slide. Alternatively, the three-dimensional shapeof the defect can be determined, as described above, and then brokendown into two dimensional slices for the rapid prototyping process. Theadvantage of using the three-dimensional model is that thetwo-dimensional slices used for the rapid prototyping machine can bealong the same plane as the two-dimensional images taken or along adifferent plane altogether.

Rapid prototyping can be combined or used in conjunction with castingtechniques. For example, a shell or container with inner dimensionscorresponding to an articular repair system can be made using rapidprototyping. Plastic or wax-like materials are typically used for thispurpose. The inside of the container can subsequently be coated, forexample with a ceramic, for subsequent casting. Using this process,personalized casts can be generated.

Rapid prototyping can be used for producing articular repair systems.Rapid prototyping can be performed at a manufacturing facility.Alternatively, it may be performed in the operating room after anintraoperative measurement has been performed.

III. Kits

One or more of the implants described above can be combined together ina kit such that the surgeon can select the implants to be used duringsurgery.

The foregoing description of embodiments of the present invention hasbeen provided for the purposes of illustration and description. It isnot intended to be exhaustive or to limit the invention to the preciseforms disclosed. Many modifications and variations will be apparent tothe practitioner skilled in the art. The embodiments were chosen anddescribed in order to best explain the principles of the invention andits practical application, thereby enabling others skilled in the art tounderstand the invention and the various embodiments and with variousmodifications that are suited to the particular use contemplated. It isintended that the scope of the invention be defined by the followingclaims equivalents thereof.

What is claimed:
 1. An implant for implantation on a patient's femur,the implant comprising: (a) a condylar portion having (i) a condylarbone-facing implant surface configured to oppose at least a portion of afemoral condyle of the patient's femur and (ii) a condylar articularimplant surface configured to articulate with at least a portion of atibial surface; and (b) a trochlear portion having (i) a bone-facingimplant surface configured to oppose at least a portion of a trochleaand (ii) an articular implant surface configured to articulate with atleast a portion of a patellar surface, when the implant is implanted onthe patient's femur; wherein the condylar portion and the trochlearportion are formed as a single component; and wherein at least a portionof one of the bone-facing implant surfaces comprises a chamfer cutsurface to abut a bone cut surface and wherein the condylar portion isconfigured to have at least portions of the patient's femoral shape andinclude patient-specific shape information derived from electronic imagedata of the femoral condyle.
 2. The implant of claim 1, wherein theimplant is selected from a library of implants and further manipulatedto match the patient's femur.
 3. The implant of claim 1, wherein theimplant has only one condylar portion.
 4. The implant of claim 1,wherein the condylar portion is a first condylar portion and the implantfurther comprises a second condylar portion, wherein the first andsecond condylar portions are disposed on opposite sides of the trochlearportion.
 5. The implant of claim 1, wherein the bone-facing implantsurface of the trochlear portion bone is configured to abut at least aportion of uncut trochlear bone upon implantation of the implant.
 6. Theimplant of claim 1, wherein the bone-facing implant surface of thetrochlear portion bone is configured to abut at least a portion of cuttrochlear bone upon implantation of the implant.
 7. The implant of claim1, wherein the condylar portion is configured to have at least portionsof the patient's femoral cartilage shape.
 8. The implant of claim 1,wherein the condylar portion is configured to have at least portions ofthe patient's femoral subchondral bone shape.
 9. The implant of claim 1,wherein at least a portion of the outer shape of the condylar portion ofthe implant is derived based on a tibial component shape.
 10. Theimplant of claim 1, wherein at least a portion of the outer shape of thecondylar portion of the implant is a reflection of the tibial shape ofan implant component.
 11. The implant of claim 1, wherein at least aportion of the outer shape of the condylar portion of the implant isderived based on a desired tibiofemoral contact area.
 12. A method ofmaking the implant of claim 1, including shaping the implant using a3-dimensional representation of a cartilage surface of the patient'sfemur.
 13. A method of making the implant of claim 1, including shapingthe implant using a 3-dimensional representation of a subchondral bonesurface of the patient's femur.
 14. A method of making the implant ofclaim 1, including manufacturing the implant using at least one of aNURBS surface and a parametric surface of polygon.
 15. A method ofmaking the implant of claim 1, including manufacturing the implant usinga shell generated with a rapid prototyping system.
 16. An implant forimplantation on a patient's femur, the implant comprising: (a) acondylar portion having (i) a condylar bone-facing implant surfaceconfigured to oppose at least a portion of a femoral condyle of thepatient's femur and (ii) a condylar articular implant surface configuredto articulate with at least a portion of a tibial surface; and (b) atrochlear portion having (i) a bone-facing implant surface configured tooppose at least a portion of a trochlea and (ii) an articular implantsurface configured to articulate with at least a portion of a patellarsurface, when the implant is implanted on the patient's femur; andwherein at least a portion of one of the bone-facing implant surfacescomprises chamfer cut surface to abut a bone cut surface and wherein thecondylar portion is configured to match a corrected joint anatomy of thepatient and include patient-specific shape information derived fromelectronic image data of the femoral condyle.
 17. The implant of claim16, wherein the corrected joint anatomy includes one or more bone cuts.18. An implant for implantation on a patient's femur, the implantcomprising: (a) a condylar portion having (i) a condylar bone-facingimplant surface configured to oppose at least a portion of a femoralcondyle of the patient's femur and (ii) a condylar articular implantsurface configured to articulate with at least a portion of a tibialsurface; and (b) a trochlear portion having (i) a bone-facing implantsurface configured to oppose at least a portion of a trochlea and (ii)an articular implant surface configured to articulate with at least aportion of a patellar surface, when the implant is implanted on thepatient's femur; and wherein at least a portion of one of thebone-facing implant surfaces comprises a chamfer cut surface to abut abone cut surface and wherein the condylar portion is configured to haveat least portions of the patient's femoral shape and includepatient-specific information derived from electronic image data of thefemoral condyle, wherein the implant is selected from a library ofimplants and further manipulated to match the patient's femur.
 19. Theimplant of claim 18, wherein the library includes implants of varioussizes.
 20. The implant of claim 18, wherein the library includesimplants of various shapes.
 21. The implant of claim 18, wherein thelibrary includes implants of various thicknesses.
 22. The implant ofclaim 18, wherein the implant selected from the library is shaped bymechanical abrasion.
 23. The implant of claim 18, wherein the implantselected from the library is shaped by, at least in part, an automatedprocess.
 24. The implant of claim 18, wherein the implant selected fromthe library is shaped by, at least in part, a manual process.